1. Field of the Invention
Exemplary embodiments of the present invention relate to a vent valve for a fuel tank and, particularly, to a noiseproof vent valve for a fuel tank, capable of radically blocking occurrence of contact noise by preventing a float moving up and down in the fuel tank due to the fluctuation of fuel from coming into contact with the bottom of a valve body.
2. Description of Related Art
In general, vent valves for fuel tanks are be closed when an amount of fuel injected into a fuel tank reaches a fixed value, thereby functioning to prevent the fuel from being further injected into the fuel tank.
To this end, the vent valve is equipped with a float that is raised by a buoyant force of the fuel when a filled level of the fuel injected into the fuel tank reaches a preset range. Thus, the float is operated to block an upper side of a valve body, thereby preventing the fuel from being further injected from a fuel injection pipe.
FIG. 6A shows an internal configuration of a typical vent valve.
As shown, the vent valve is made up of a ball seat 2 that is installed along with a ball on an upper side of a valve body 1 to which a fuel injection pipe is coupled, a float 3 that occupies a space of the valve body 1 and is raised by a buoyant force of fuel in an exceeded state of injected fuel, and a spring 4 that elastically supports the float 3 using a lower end 5 of the valve body 1.
The spring 4 is subjected to compressive deformation by the float 3 moving down.
The lower end 5 is integrally formed with the valve body 1. However, the lower end 5 may be separately manufactured as needed, and then be coupled to the valve body 1.
The valve body 1 and the float 3 are typically formed of a plastic material.
When the fuel is injected and in a state in which an amount of fuel is not in a full state, the ball seat 2 installed on the upper side of the valve body 1 pushes down the float 3 while compressing the spring 4 under a gravitational force, thereby opening a vent passage. In contrast, the float 3 is raised to push up the ball along with the ball seat 2 by a buoyant force of the fuel, thereby closing the vent passage to block inflow of the fuel.
However, as described above, the float 3 is elastically supported by the spring 4 placed on the lower end 5 constituting the bottom of the valve body 1, and no support structure is applied between the lower end of the float 3 and the lower end 5 of the valve body 1. As such, there is no alternative but to have structural limitation in that noise occurs.
FIG. 6B shows another example of the aforementioned noise occurring at the vent valve. As shown, the float 3 moves between an initial position A and a displaced position B due to an intermittent buoyant force caused by the fluctuation of the fuel in the fuel tank during the traveling of a vehicle. The float 3 comes into contact with the lower end 5 at the displaced position B to which it moves down (denoted by “Ka”). Thereby, “clicking” contact noise continues to occur.
This contact noise gives very unpleasant sensation to a driver. Especially, in the case of hybrid vehicles, even low noise that is caused by a valve when an engine is turned off or when a motor is turned on and is introduced into an interior of the vehicle is an offensive sound. In this state, the introduction of the “clicking” contact noise of the vent valve into the interior of the vehicle may lead to the dissatisfaction of consumers.
Although such noise is irrelevant to operation and performance, it amplifies the dissatisfaction of consumers. Consequently, this noise has no alternative but to exert a great influence on the merchantability of the vehicle.